Down's Syndrome (DS) children show marked problems in language and speech development. The primary goal of this proposal is to study specific problems related to the development of a linguistic sound system in DS children and to isolate precursors of these problems in infancy. The proposed research will provide detailed information on the pattern of development of phonological skills in children with DS by contrasting results from assessments of speech perception and production with similar results derived from normal children at similar stages of linguistic development. In specific, perception of steady-state and dynamically changing sppech patterns will be compared within DS and normal populations. The major hypothesis to be investigated is that DS children have relatively greater difficulty discriminating between speech sounds differentiated by rapidly changing spectral patterns than stimuli differing in steady-state components. Thse studies will employ high amplitude sucking, visually reinforced speech discrimination and heart rate methodologies for studies of discrimination and lateralization. Similar stimuli will be explored in linguistically complex real speech discrimination tasks with older DS and normal children using a tangible reinforcement paradigm. Studies of speech production in DS and normal infants will focus on occurrence, stability, and timing of canonical speech-like sounds. The major hypothesis to be investigated is that DS infants use fewer different canonical forms, exhibit significantly different syllable timing features and do not use volaizations to achieve various communicative functions to the extent that normal children do. The studies will involve tape recordings plus transcription, instrumental acoustic analysis and coding of communicative competence. Two studies of specific early intervention in speech discrimination and production with DS infants will explore a developmentally rational intervention model for DS infants.